McCaw Hall’s enormous stage is disconcertingly empty on a Friday afternoon, though its spacious backstage is a wild dream of Wagnerian proportions.

Tucked away, well out of sight from an audience’s perspective, are splendid and massive set pieces from Seattle Opera’s “Der Ring des Nibelungen.” During the four operas comprising Richard Wagner’s epic cycle, each will be rolled out at one point or another.

But at this moment, the mountainside set from Act Three of “Die Walküre”— upon which Wotan will summon Norse demigod Loge to encircle a sleeping Brünnhilde with protective fire — is being pushed front and center on stage and will soon light up like a birthday cake.

From his small perch on the side of stage right, Seattle Opera’s longtime fire designer, Charles Tim Buck, controls a software program setting ablaze the many burners concealed in rocky crevices. He tests the networks of gas lines, valves and igniters snaking through individual sections of the mountain’s face and up into surrounding trees, then burns them all simultaneously. In a darkened theater, and from a few feet away, it’s a spectacular vision.

“The way I programmed the scene, we picked a certain spot where Wotan throws his spear down and calls for Loge to start the fire,” says Buck. “It starts in one spot and jumps and spreads around the cliff until it reaches the trees, then the trees go up and that’s when the curtain goes down. This fire was conceived as a living, growing thing.”

There is fire throughout Seattle Opera’s “Ring,” including scenes in “Siegfried” and “Götterdämmerung.” The biggest fire effect in the current version of the cycle — mounted every four years since 2001 — is the closing scene of “Die Walküre.”

For the 1985-95 version, Buck created an enormous fire, about 32 feet high and 27 feet wide, for the climactic “End of the World” sequence in “Götterdämmerung.” The goal, that time, was impressiveness and vastness. By contrast, the growing fire in “Die Walküre” is more of a rising crescendo of drama.

But in any scene, Buck — who also serves as Seattle Opera’s flight-technical director, getting the “Ring’s” singing Rhine Daughters in the air — says a fire effect “is not what the show is about. The fire is designed to assist in telling the story.”

Buck, 63, became Seattle Opera’s master stage carpenter in 1990, following years of toiling backstage on concert and ballet tours.

Following a stint in the military, where he became an explosives expert, he earned his master’s degree in technical theater.

Buck has employed fire effects and pyrotechnics in several Seattle Opera productions. A 2004 “Ariadne auf Naxos” included three minutes of indoor fireworks.

Buck’s expertise with fire design and pyrotechnics found its way into several A-list Hollywood features, including Steven Spielberg’s “Always,” Lawrence Kasdan’s “I Love You to Death” and the “Die Hard” series.

Buck says it’s crucial to remain vigilant about the destructive power of fire.

“After a while, you think, ‘This is no big deal.’ Then fire says, ‘You need a little humility.’ When you get overconfident and cocky, you do things you shouldn’t do, or you forget to do things you should have done. You have to keep your mind in the game. Once a fire gets started, it wants to consume, it wants to grow.”